A horse is not a registered Icelandic unless it holds a passport from an Icelandic horse breed society such as the IHSGB or any other FEIF-recognised organisation. The IHSGB is a Passport Issuing Organisation, authorised by DEFRA. To be registered, horses must be able to trace their ancestry in an unbroken line back to Iceland. It is not possible to register part-bred Icelandics, and they cannot compete in competitions for Icelandic horses. The studbook of Icelandic horses in the UK is linked to WorldFengur, the international database of Icelandic horses worldwide. All IHSGB members have free access to this fascinating resource.

There are a number of breeders of Icelandic horses in the United Kingdom, and there are several good stallions in the country. Approximately 20 foals are born each year, with some being imported in utero in mares from Iceland and Europe.

The IHSGB organises breeding assessments for Icelandic horses in the UK, where horses are judged by a minimum of two judges against the international breed standard for Icelandic horses known as the FIZO. Horses are awarded marks out of 10 for conformation and rideability, and those with a mark of 8.00 or higher are known as First Prize horses. All results are held in WorldFengur. All stallions used for breeding should be assessed once they are trained to ride.